Hearts of Mutagen
by NyanWolf
Summary: What if Leo had gone to Coney island alone, and what could have happened if Bebop and Rocksteady had been just a few minutes later? Now, Leo may have to choose between the one he loves and his own brothers. Karai x Leo pairing! Warning, contains spoilers for the Pig and Rhino episode.
1. Chapter 1

**This is based on the episode Pig and Rhino. Guys, please no hate since this is my first TMNT fanfic. Basically this is a different take on the episode -I changed almost everything- and I hope you all enjoy! Reviews/constructive criticism are appreciated and wanted. This is a Karai x Leo pairing.**

**DISCLAIMER:I do not own TMNT!**

* * *

"Karai!" Leo called out. He was searching the Coney Island Amusement Park. Mikey had wanted to come, but Leo had sent him with Casey and Raph. He didn't know why, but as soon as Donnie had pulled up Coney Island on the computer, Leo had known Karai would be there. There! A flash of white scales. Leo ran toward the old rollercoaster and heard a slight hiss. He turned a corner and there she was.

"Karai..." Leo whispered. She looked so..._different._ It hurt Leo to look at her, knowing he had caused her change. She hissed delicately.

"Leo?" She rasped. Leo nodded gently, slowly advancing toward her. She backed against the railing of the coaster.

"No, it's ok. I want to help. Donnie...Donnie made this. I - I think that it can help you," He held up the retro-mutagen. Karai slowly moved closer. Leo sprayed some around Karai, and watched as...nothing. Nothing happened.

"It...it didn't work..." Leo's face fell. He felt something cold and smooth wrap around his arm. Karai's own snake-headed hand was squeezing his slightly, forcing him to look her in the eye.

"Goodbye Leo," She choked out. Leo cupped her face in his hand. He looked into those eyes that were like twin pools of moonlit ice. Even like this, she was beautiful, and not just on the outside. No, she had more. A strength, one made of the strongest steel, armored her soul and radiated intelligence, understanding.

"Please, you can come home with us. With me! Don't you want to see Master Splinter again? Your real father?" Leo pleaded. She shook her head.

"My mind...is going...dangerous...goodbye," She hissed. Leo caught the teardrop running down her silvery scales. He took a deep breath, then wrapped his strong arms around her and pulled her into an embrace long due. He closed his eyes, hoping that if he did, it would make the moment last longer. Karai pulled away all too soon.

"Leo...if you had to pick...between...with me...and brothers...which?" She stuttered. Leo looked at her. Karai or his brothers? What did that even mean? He couldn't pick...surely she wasn't asking him to actually pick, right? She waited. One long moment of tension followed another. Finally Leo spoke.

"I love my brothers because they are my family. But...I also...I couldn't bare to loose you either...I don't know," He sighed.

"They could change you back...if you wanted," She said, slithering closer.

"What?" Karai titled her face up to meet Leo's lips. She hugged him, pulling him closer, and Leo hugged back. Her fangs were sharp, but Leo didn't feel them. He didn't feel anything. It was just him and Karai. Not snake Karai, but the real, true girl. Suddenly, she froze. They could both hear voices. Leo cautioned for her to stay back, then moved on ninja feet to the source of the noise.

It was a Zeck, now a pig, and Steranko, now a rhino.

"Come on out turtle, vee know you is here," Steranko said in his accent. Leo turned to Karai and found no one. _They could change you back..._ He knew what she meant now. Already he could feel the mutagen from Karai's fangs pumping through his veins. But now, he realized, we can be together. With a guilty burst of energy, Leo shot out from his hiding place and confronted the pig and rhino.

"You want me? Come get me!" He yelled.

"Uh-uh! Zeck knows you did not just do that!" Zeck squealed as Leo sliced off an inch of his Mohawk. It was then that Steranko revealed Leo's brothers and friends, locked away. Leo froze.

"That is right turtle," He grinned, rolling his R, "You either surrender, or vatch your friends die!"

"You just got owned homie!" Zeck called out. Leo hissed. He actually _hissed!_ Narrowing his eyes, his pupils squeezed into vertical slits. Leo charged with more speed and agility than ever. He could feel a twinge in his upper gums as fangs began to grow, fully equipped with poison sacs. Leo flipped high in the air, and came down with his jaw latched onto Steranko's head.

The rhino bucked and screamed in panic, but soon fell unconscious, a crumpled heap on the ground. Zeck followed and Leo had Cacey, April, and his brothers soon freed. While Raph and Cacey were making sure the baddies were down (By kicking them in the face repeatedly) and Mickey was coming up with names, Donnie and April stayed with Leo.

"Did you find her?" Donnie asked. Leo hesitated.

"She was here, I saw her leave, but before I could follow her, _they_ showed up," Leo lied, indicating to the newly dubbed "Bebop and Rocksteady."

"Leo, what happened to your hand?" April asked suddenly, Leo looked to see what she was talking about. There was a small patch of silvery-white scales across the back of his hand.

"It almost looks like some kind of reaction. Maybe allergic or something?" Donnie guessed.

"Yeah," Leo laughed nervously, "Or something."

* * *

**Ok, so I'm leaning on making this a one shot, but I might continue if people like it. Again, please review! And by the way, it is hard to write from Leo's pov, since Mikey is my favorite, but I tried! Tell me how I did! Anyway...**

**Wolf out...**


	2. Chapter 2

**Ok so I wasn't planning on continuing this story, but you guys seemed to really like it so...yeah! I hope you all enjoy, and thanks to all the people to reviewed or followed or favorite the first chapter.**

**Reviewers:**

**StarTraveler: Thanks that means a lot. And yeah I nearly cried as well during the episode, usually I don't do pairings but Karai and Leo were made for each other.**

**Insanity21: Thanks for the review! I'm happy your liking the story.**

**DP fanboy: Thanks! I'll totally write more, and I usually update pretty frequently.**

**All my other reviewers: I have read your reviews and it made my day to see them, thanks for reviewing and I hope you continue to do so. Enjoy!**

**DISCLAIMER: I don't own TMNT!**

* * *

Back in the sewers, Leo tossed and turned in bed. He suddenly shot up straight, panting and sweating. He looked at the bandage on his hand, Donnie had made him wear it so that Leo wouldn't mess with his "rash." He realized he was hungry. Leo flicked his tongue out of his mouth, smelling the air for something he could eat. There it was, _meat._ Stomach growling, Leo rose out of bed and followed the smell. So much meat. He could sense it, smell it, taste it. He stopped by a door, opened it.

Leo carefully got down on his belly. Then he army-crawled to an orange bed in the middle of the room. As he crawled, his body twisted and curved in odd ways, almost like how a snake slithers. Anyway, Leo pulled himself up by the side of the bed. _Meat...Turtle._ He opened his mouth wider than should have been possible for him. The familiar twang in his mouth indicated that his poison sacs were refilling. Closer, closer. Right above the sleeping turtle's neck. He couldn't help himself, Leo let out a content hiss.

"Wha-Who is it? Leo? What's up dude?" Mikey sat up in his bed, squinting in the darkness. Leo froze, staring at Mikey with his mouth still open.

"Hungryyssss" Leo hissed again, preparing to stab his fangs into Mikey's neck.

"Why didn't you say so dude! Come on!" Mikey jumped out of bed just as Leo's head snapped forward to bite. His jaws closed around air. Before he could even register what happened, Mikey had him by the arm and was dragging him towards the kitchen.

"Ok lets see...cereal?" Mikey asked, rooting through the pantry. Leo narrowed his eyes, targeting his prey. Mikey chuckled nervously.

"Right no cereal. Ice cream?" Mikey moved to the fridge just as Leo was lunging at the back of his neck. Leo ate air again and hissed in frustration.

"No ice cream? Really? Wait wait! I know. How 'bout PIZZA!" Mikey yelled, holding out a pizza box. Leo's face twitched, his poison sacs _needed_ to be emptied!

"Aargh!" He grunted in anger. If the turtle would just stand still!

"But you love pizza," Mikey's face fell. Leo snatched away the pizza box with snake speed and sunk his fangs into it, moaning in relief as his fangs emptied. Leo kept biting until every last drop of poison was on that box, his eyes rolling up in pleasure. Mikey stared at him.

"Wow, you were hungry. Um, you know you have to open the box to get the pizza out, right dude?" Mikey asked. Leo swung his head around at Mikey and hissed. Mikey yelped and jumped up on the counter.

"Haha, that's cool bro, you can eat the box if you want!" He said. Leo unhooked the soggy box from his fangs and threw it out. Then he turned and stiffly walked back to his bedroom, got in bed and completely passed out.

* * *

"Aaah! I slept like a baby, completely refreshed!" Leo announced as he walked into the living area the next morning. Mikey, Donnie, Raph, Casey, and April were already waiting for him. They all froze and looked up when Leo entered.

"Why are you guys staring at me like that?" Leo asked.

"Dude...you don't remember?" Mikey asked in a low tone.

"Uh...what? Is this like a joke or something?" Leo answered.

"Mikey says you were acting weird last night," Donnie said in concern.

"Weird like how?" Leo came over, sitting on the floor by Mikey, who scooted slightly away.

"Weird like eating a pizza box. Is there something you're not telling us Leo?" Raph said. Leo shook his head.

"Mikey must've had a nightmare. I was in bed the whole night. And I think I would remember eating a pizza box," He pointed out.

"Maybe...Are you sure you're ok though? You seemed pretty out of it when karai got away yesterday," April muttered.

"I _said _I'm FINE!" Leo shrieked, standing up. He grabbed April's shoulder, pulling her up roughly. April grunted in surprised pain. Leo only hissed.

"Dude what's gotten into you!" Mikey yelled.

"Leo stop, we don't want to hurt you!" Casey joined the mixture of screams and gasps.

"Leo?" April whimpered. Leo stopped. What was he doing? For a moment everyone was frozen in place, then Leo released April and ran out of the room.

"Leo!" Raph shouted. Donnie put a hand on his shoulder.

"Let him go Raph. He has to come back eventually," He sighed.

* * *

Leo panted as he ran deep into the sewer system. Finally he collapsed on the ground, breathing heavily. When had running gotten so hard?

"Leo." Leo turned to see Karai slithering towards him.

"You! What did you do to me?" Leo yelled even though he knew exactly what she'd done.

"Leo," Karai hissed again, "Together now...Don't you...want?"

"Of course I do. But...not like this. What if I hurt someone? Hurt my family?"

"I...your family...now."

"But..."

"We are...pair...two...of a kind...family...alone."

"This is why you hide away isn't it? To prevent hurting anyone. Smart."

"Are...you happy...right now?"

"Only because I'm with you."

"Then...stay...like this...with me." She flicked her tongue, gently caressing his face. Leo shuffled closer. He slung an arm around her, and cradled her like that. Her snake body pressed against his shell. He was surprised at how warm she was, how soft.

"I'll have to go soon," Leo sighed, wishing that they could stay like this forever.

"Then enjoy...the moment," Karai wrapped her tail around Leo, pulling his face into hers. For a time, fangs met fangs and lips met lips. A high pitched squeal came from a tunnel, shattering their kiss. Leo swiveled his head around to the sound of footsteps running away. Leo looked at karai and gestured for her to leave.

"Back here...Tomorrow?" She asked as she slithered away.

"I'll try," Leo assured her as he ran over to the spot from where the sound had come. He inhaled sharply and paled. On the floor of the sewer, sitting in perpetual stillness, was a single hockey mask, designed like a skull.

* * *

**Right so I hoped you guys enjoyed, I actually really like writing this story. I'm thinking that I'll update on Fridays. Probably. Which means that if I decide to do that, my next update will be this Friday. Anyway...**

**Wolf out...**


	3. Chapter 3

**Here it is, not too much happens in this chapter, but it should be enough. Thanks again to all my awesome reviewers, you guys all rule!**

**StarTraveler: Yup, Leo's transformation might be slow, but it is noticeable and he only has a little Leo left in him. Anyway, I hope you enjoy this 'mostly Casey' chapter.**

**Kuronique Misaki: Thanks for reviewing, I'm glad you like the story.**

**prettyshon10: You said you couldn't wait, so here is the next chapter! Enjoy!**

**Insanity21: Thanks! I'm super happy you found it awesome and cute, and yes, Karai _really_ wants Leo! XD  
**

**DISCLAIMER: I don't own TMNT**

* * *

"Guys!" The others were lounging around when a breathless Casey burst in.

"What is it Casey?" April asked, slight concern in her voice. Casey stumbled into the room and sat down heavily on the couch. His eyes were wide and his face was pale. Everyone gathered around him as he started to speak.

"Leo...Karai...Karai did something to him! And then they...they...she...she," Casey was looking for a way to say it, but he couldn't. They couldn't have really..._kissed_, could they? No. No matter what that witch did to him, Leo would never!

"Just say it Casey!" Raph shouted, bringing him back to reality.

"She bit...his face...yeah..." Casey finished. Donnie bit his lip in thought.

"Hmm, if Karai was mutated into a snake, maybe her fangs have some sort of mutagen-like qualities that might be changing Leo...especially if she's been biting him..." He said.

"You mean..." Mikey started. Donnie nodded.

"Karai might be mutating Leo."

"What can we do?" April asked.

"Well I might be able to create an antidote, but I would need a blood sample," Donnie mused.

"Then what are we waiting for, let's go find him!" Raph said.

"I don't know Raph, Leo seemed kind of...unstable," Casey muttered.

"Well we can't just stand around waiting for him to go all snake on us!" Raph retorted.

"Casey's right, if we confront Leo, he might attack us or something. We need to do this right, don't let him know that we know anything," April reasoned.

"Hey Casey," Mikey started casually, "What happened to your mask dude?"

"What do you mean, I have it right...here?" Casey frantically patted himself down as his eyes bulged in panic.

"Casey...you didn't lose it in the sewers...did you?" Raph said very slowly, as if explaining a difficult concept to a kindergartener. Casey smiled nervously, rubbing the back of his neck with one hand.

"Um...maybe?" He chuckled. Everyone groaned.

"Oh come on! What are the chances that Leo even saw it?"

"CASEY!" An extremely angry Leo barged in holding the skull-shaped hockey mask.

"Apparently, REALLY GOOD CHANCES!" Donnie yelled.

"Shh! We can still play it dumb," April pressed her finger against Donnie's lips, causing Donnie's pupils to swell into heart shapes.

"CASEY JONES WHEN I GET MY HANDS ON YOU!" Leo screeched, marching straight for Casey. The whites of his eyes turned a blackish-green and his own pupils became vertical slits.

"Whoa, come down Leo!" Mikey jumped on his back, only to be knocked into the wall.

"Mikey!" Raph shouted.

"Wait a second...If Leo is turning snake then that means...Guys! Hold him off, I'll be back!" Donnie ran for his lab, leaving everyone else to fight off the blue-clad turtle. Casey brought out his hockey stick.

"What are you doing?" April asked.

"Don't worry Red, Casey Jones can handle anything!" Casey grinned as he ran at Leo. Raph unsheathed his sai.

"Ugh, sorry Leo," He muttered, joining the fight. Mikey stood next to April and was about to leap in when Casey was sent flying into him.

"Leo!" Donnie came rushing in with something in his hands. It looked like a canister of ice cubes.

"Ice? What are you gonna do, throw them on the floor and hope he slips?" Raph shouted as he dodged Leo's attacks.

"Actually Raph, these are cubes of concentrated nitrogen, extremely cold and normally used for -" Donnie ranted.

"Donnie, whatever you're going to do, do it now!" April screamed.

"Heh, heh right. Hey Leo, over here!" Donnie flicked a switch and a cold gas shout out of the mouth of the canister. The gas, upon touching Leo's arm, froze into a sheet of ice and covered half of the turtle's arm. Leo shuddered, then slowed, finally falling to the ground curled in a ball.

"Donatello I love your mind!" Donnie whispered gleefully.

"You killed him!" Mikey yelled in horror.

"What? No! Like I said, the nitrogen is extremely cold, and since Leo has been showing snake-like instincts, he reacted the way any snake would. He became drowsy and slow."

"Aren't you guys cold-blooded too?" April pointed out.

"Actually we have blood very similar to that of a human," Donnie laughed as he pulled out a needle and drew some of Leo's blood.

"You better get that stuff tested Donnie, we'll watch Leo," Raph said. Donnie nodded and started towards his lab.

"Don't worry Raph, if anyone can fix Leo, Donnie can," Mikey said hopefully, sitting next to his older brother.

"I hope you're right Mikey," Raph sighed, "I hope you're right."

* * *

**Yeah, Raph is genuinely worried, but hopefully Mikey can make him feel better! By the way, did anyone catch Donnie's quote from "Casey Jones VS the Underworld," because I just watched it and I loved that one quote so much that I decided to steal it! Can you guys find it? Anyway...**

**Wolf out... **


	4. Chapter 4

**Ok so I updated early because I probably won't be able to write much tomorrow. Road trip! Hope you guys all enjoy and thanks to my reviewers, new and old!**

**Reviewers:**

**Insanity21: Thanks so much! And you are right about Karai coming to get Leo! Enjoy!**

**WOLFJADE28: Glad you like the story and that you got the quote! Thanks for reviewing and I sincerely hope you keep doing so! And (you can probably tell from my username) I love wolves, cool name!**

**StarTraveler: True, true...for now! Dun Dun Dun! But yeah, thanks for reviewing and enjoy!**

* * *

Donnie was walking through his lab, looking for something that could help him with a cure. He looked up at the sound of Raph coming in.

"Oh, hey Raph," He greeted his brother distractedly.

"Hey Don. Have you found an antidote yet?"

"Not yet..."

"Oh. Good. That will make things easier for us," Raph said. Donnie looked at him in confusion. Raph sneered, showing tiny, white fangs.

"Raph?" Donnie whispered. Raph's eyes were slits as he hissed. His body grew thinner and elongated. Bright, red scales swept down his body in waves and his legs melted together into one skinny tail. Within seconds, a huge red snake stood before Donnie.

"Yaaaaaaaaaaaahhhh!" Donnie screamed, backing into a corner.

"Donnie? Why're you screaming dude?" Mikey walked in, completely unfazed by the snake.

"Mikey! Get back! There's something seriously wrong with Raph!" Donnie yelled. Mikey looked up at Raph, noticing him for the first time.

"What's the matter bro? Don't you recognize your own brothers?" Mikey hissed as orange scales etched themselves onto his skin. Now another, slightly smaller orange snake was rearing up next to the red one. Donnie cowered in his lab. Finally another snake slithered in. Bigger than the others. A massive blue one with glittering white fangs. Donnie stared.

"Leo?" He gasped. Then Donnie felt a tingling sensation running through his body, his skin started to itch and crawl. He looked down to see purple lines scrathing into his skin. It was almost like a marker tattoo, until the pattern seemed to raise itself off his skin and harden into real scales. He felt himself growing taller and taller and felt sharp fangs ripping through his gums where his gap was.

"Isn't this great Don?" Leo asked. "Now we can all be one big happy family!" Donnie sucked in air in short breaths. The world blurred as the other snakes pressed in around him.

"AAAAAAAAAAAHHHHH!" Donnie woke up in a panic and fell out of his chair. In a frenzy of spastic movement, he patted himself down to check for scales and pressed his tongue to the gap in his teeth. Breathing a sigh of relief, he looked up to his desk, where he had fallen asleep working out a formula.

* * *

Meanwhile, Leo was coming to. He moaned, both from grogginess, and because his mouth felt like it was about to explode. He sat up and went to his bedroom door. Locked! Suddenly, Leo remembered everything that had happened. He started hyperventilating, his brothers knew! He had tried to hurt them!

_Tap, tap, tap!_ Leo looked to his window to see Karai tapping on the glass with her tail.

"Come...on!" She rasped. Leo looked back toward the door, then sighed. He grabbed his two ninjato and sliced away the glass. He slipped through and followed Karai back into the sewers. When they came to a manhole, she stopped.

"Wait, we're going topside?" Leo asked incredulously. She smiled.

"Show...you...burrow..." She pulled him up into New York and started leading him towards Coney Island.

"Um, burrow?"

"Nest..."

"Nest? Karai, what are you talking about?" Leo said suspiciously.

"When you fully...change...new home..." She cooed in his ear. Finally they made it back to the place it all began. Karai pulled him back to the rollercoaster, then allowed him to sit. Leo looked around. A huge pile of dirt and leaves and sticks was stacked up against the railing. She dived into the pile and lay there, waiting for Leo. He clumsily hauled himself up.

It was surprisingly comfortable. Karai hissed lovingly.

"I attacked them..." Leo sighed.

"Yes...that will happen..."

"I was thinking, maybe if they become like us too then -"

"NO! We...stay...together! Brother's interfere!" She snarled.

"Ok, ok. Sorry...My fangs seriously need to be emptied," Leo changed the subject.

"Good...teach you...how to eat!" She seemed pleased. Karai reached around the ground with her tail until she pulled something up with a squeak. Leo gagged. In her tail, were two squirming _live_ rats.

"Master Splinter..." He whispered in terror. Karai snapped her head up.

"What?"

"N-n-nothing," Leo tried smiling. She plopped a rat into his hands and kept one for herself.

"Now...we eat!" She instructed. She clutched her rat in her tail and bit into it's neck with an audible crunch. The rodent's head was no more. Leo stared at his rat. It looked at him with pleading eyes. He as going to let it go, pretend he dropped it. Then the smell of blood overcame his senses._ Just one little bite..._

* * *

**Sorry it's slightly short, but I hope you all enjoyed it anyway! As I wrote this chapter I realized that a real snake would be in heaven in the Lair. Between turtles and a giant rat, yeah...Anyway...**

**Wolf out...**


	5. Chapter 5

**By the way guys, I have taken Hun from Casey Jones VS the Underworld and put him into this setting. Which means that Hun is kind of like a time traveler, being from a more recent episode and all.**

**Reviewers:**

**StarTraveler: Nice. Even though I don't know how you could eat during the rat part. And I was really hoping to scare some people during the nightmare, you're not the only one! :3**

**WOLFJADE28: Ha ha! That's awesome, but I won't deny that this is a freaky story (especially this chapter)! And I kinda like the name Count Leoviper...**

**DP fanboy: Heck yeah she does! Thanks for reviewing!**

**My guest reviewer: Thanks and I update every Friday!**

* * *

"Master Shredder, Karai is still missing," Steranko (Rocksteady) bowed his head next to Zeck (Bebop) while their master watched from atop his staircase. Shredder sighed in contempt.

"Tell me..._Rocksteady..._how many times have you and your miserable excuse for a partner, failed me?" He snarled.

"Um...a lot?" Bebop offered. Within seconds he was on the floor, clutching his face from where Shredder had lashed out.

"I tire of your insufferable mockery! Thankfully, I have acquired a more _useful_ aid." A tall, broad shouldered man with tinted glasses stepped out from behind Shredder. He blew a strand of jet black hair away from his face, and smiled threateningly. His long arms were tattooed and he wore all black.

"Master Shredder, vat is this? You cannot simply get rid of us!" Rocksteady growled.

"On the contrary, I have hired Hun to be your teacher. He will aid you in your mission to find my daughter. Think of it as a test, and if he does well, he will gain independence. And my trust. If he tells me you two have done well, I will de-mutate you. And spare your lives," Shredder trailed off maliciously.

"Hello students. I can already tell this will prove...amusing," Hun laughed, a devilish glint in his eye.

* * *

"Leo woke up with a dull pain in his neck and shoulders. His back ached and his stomach was a hunk of ice. He felt warm though, and didn't want to face the cool morning air. It was weird however, how his blanket was so smooth. For a moment, he fully believed he was in his bed in the Lair. At least until a half itch, half tickle started up in the back of his throat and traveled into his nose.

"Hept...Ah...Ah...AH-CHOO!" He sneezed, allowing his eyes to open. A long silvery-blue tail was lying on top of him like a blanket, the tip barely brushing his nose. Briefly, he panicked that he was trapped in some sort of snake pit before remembering Karai. But on looking around with bleary, sleep-clogged eyes, he found no sign of his scaly girlfriend. Which could only mean...

"AAAAAAAAAAAAAAAAAAH!" Leo screamed as he looked down on the tail, the tail that was his! Everything under his waistline was covered in scales and sloped down to a point. He stayed like that,screaming, for almost a minute before he ran out of breath. Then came the hyperventilating, and the panicking, and the rocking back and forth (Which was hard to do with a tail) and finally, he touched it. It twitched at the interaction, but otherwise was still.

It was actually kind of soft and smooth, and not even wet. Leo found himself stroking it, before remembering that he was a turtle with a snake tail.

"Ok...ok...It' ok...I'm fine...It's just a...a...a _development..._I'm ok...It's all ok...Who knows...Maybe I'll be faster now...heh heh!" Leo chuckled nervously. He stetched and felt the pain in his cramped joints. He noticed that his stomach still felt funny. _Ugh, what did I eat last night?_ Leo froze.

"A rat..." He whispered, eyes wide. "I ate...a live...rat!" But it wasn't that that bothered him so much as the fact that he'd enjoyed it! He remembered now...every last bit of bloody flesh was devoured without care. He had loved every second of it! _But that wasn't me. Not really. It wasn't me. It was the snake. It was the mutation. It wasn't me because I wasn't in control. _

After he finished consoling himself, Leo decided to test out his new tail. He stumbled out of the "nest" and onto the ground. He teetered around for a second, before falling straight on his face. _Ok, let's try this again._

He pushed himself upright and flailed his arms. _Good, now how do I start this thing? Is there an 'on' button or something..._He focused, twitched the tail, and sped forward at warp speed. _Too much! Too much! _Leo sighed. This would definitely take some getting used to.

* * *

"You know you should get some sleep, right bro?" Mikey was loitering around Donnie's lab while the genius turtle worked.

"I'm fine Mikey, I don't have time for sleep!" Donnie muttered. Ever since that one nightmare, he hadn't been able to get back bed. He couldn't. What if he had the dream again!

"Hey Donnie! Did you get anything yet?" April called from where she was trying to work out where Leo had gone. They had found his room empty and his window open. Donnie just shook his head and kept typing. Raph and Casey were on the 'search and rescue team,' trying to track down Leo in the sewers.

"You do know that Mikey's right? I mean, you look horrible...no offense," April mused. It was true. Donnie had dark circles under his eyes and his green skin was a shade lighter than usual. In fact, the only reason Mikey was with them was to keep Donnie from falling asleep at his desk, where he might hit the power button on his laptop, or even the delete button.

"Thanks April. I said I'm fine, I am perfectly capable of...capable of...of..." His eyes drooped and his head started bobbing, closer and closer to the desk. HHHOOOOOOOOOOONNNNNKKKKKK! Mikey pulled out his blow horn and Donnie shot upright.

"Capable of finding a cure without sleep!" Donnie finished in a hurry.

"Great. This is going well. Really, I'm just waiting for something bad to happen!" April huffed. The lights started flashing red and an alarm sounded within the lab.

"Nice," Mikey said wryly. April shrugged apologetically.

"I'll call Raph and Casey!" Donnie shouted as he turned off his alarm.

"Hello, turtles...and girl..." A menacing, Chinese voice rang out.

"Um dudes...who is that?" Mikey whispered.

"Not sure," April whispered back. They were shielding Donnie as he made the call.

"I will answer your questions. I am called, Hun."

* * *

**And here it is, another chapter! Yay! Time traveler hype! I honestly don't have anything to say so...**

**Wolf out...**


	6. Chapter 6

**Sorry it's late and kind of shorter than normal! Writer's Block is insane! Anyway enjoy and please review!**

**Reviewers:**

**StarTraveler: Here you go, I have a feeling you'll like this chapter!  
**

**DP fanboy: Thanks and like I said, I fixed it! Enjoy!**

**WOLFJADE28: Yeah, sorrynotsorry but there is more suspense to come! I think it is mucho bien! And I'm glad I have hooked you, I like those creepy stories that you want to read, but don't want to read at the same time! Also I like your profile picture. I love My Little Pony! Just out of curiosity, have you watched season five yet?**

* * *

"They're on their way," Donnie whisper-shouted frantically.

"Yes turtles, go ahead and call your friends. All the more convenient," Hun chuckled.

"Who even are you man?" Mikey groaned.

"Must I repeat myself?"

"No, like, who _are_ you! We know your name already!" Mikey said conversationally.

"Let's just say, I am very close, to one of your worst nightmares," Hun grinned as he moved closer. Two figures stepped into the lab, a pig and a rhino.

"Wait, aren't those-" April was cut off.

"Don't say it! Just do not say Bebop!" Bebop yelled.

"Ok dude, we won't say it. But how about I say...BOOYAKASHA!" Mikey leaped onto Bebop's back, starting the fight. April ran into a flying kick that sent Rocksteady backwards. Donnie drew his staff, and advanced on Hun.

Hun just stood there, arms wide, legs spread. Donnie somersaulted into the air with the staff high above his head. He brought it down with a shout only for Hun to catch it midair. Donnie let go of the staff and dropped to the floor, sweeping a leg under Hun. Hun flipped backwards and connected his fist with Donnie's jaw.

Meanwhile, Mikey was using Bebop as a punching bag and was nearly finished with him. April was dodging and using Master Splinter's moves.

"Guysssss!" Suddenly someone else burst in. Everyone froze.

"What..." Donnie whispered. Before them stood a long, slender snake with blue armor-like plates on it's torso and a huge tail protruding out from them. It's snake-like head was aerodynamically shaped like a motor cycle helmet, with an elongated top pulled into a point.

"Help me..." The thing rasped.

"Hey where are the baddie-" Raph and Casey walked in at this exact moment and froze.

"Karai!" They both shouted.

"Wait, how do you know that-" Mikey started.

"It's her Mikey. I'm sure," Raph growled. He couldn't even begin to imagine what would happen if he was wrong. But he couldn't be wrong, right? Casey backed him up.

"Leo is in his room, asleep!" Casey said. The other two turtles and April nodded.

"Well, it seems you turtles have just made our job much easier," Hun cackled. "Get her!"

"No! Pleassssssse!" The snake, or Karai, hissed.

"Aw yeah! I'm gonna be handsome again!" Bebop ran towards Karai with Rocksteady right behind him.

"Ssssstop!" Karai slapped him with her tail.

"Hey Hun!" Donnie yelled.

"Yes little turtle?"

"I don't know why we're even fighting! We want to get rid of Karai as much as you want her! Leave us alone and we'll help you get her!"

"Hmm...you want a deal?" Hun mused. Donnie hesitated, looking at Mikey and Raph, they both nodded.

"Yeah, I do."

"Very well turtle, we will leave you, for now. But Hun doesn't need help," Hun smiled. He brought a knife out of his belt and threw it right into Karai's tail. She hissed in pain as blue-black blood burbled up. Hun ran to her, dodging her bites and swipes, bringing out a purplish cylinder. He touched her with it and let go. The cylinder expanded into a glowing purple orb, with Karai trapped inside it. She cowered against the back of it, cradling her tail.

"Now, we shall leave," Hun commanded to his comrades. They got up and followed him out.

"Are you sure we should have done that?" April asked Donnie.

"Honestly April, I don't even know anymore," Donnie sighed.

* * *

Meanwhile, Hun and his goons brought Karai back to the Shredder's lair.

"That was quick. Do you have what I asked for?" Shredder growled.

"Indeed Master Shredder, we have Karai."

"Finally, I have her," Shredder whispered as he came closer to the orb. "And your students?"

Hun looked at Bebop and Rocksteady, who were nodding eagerly.

"They merely slowed me down," Hun smiled.

"Wait, what?" Bebop cried. Shredder looked down on them.

"Send them away, I will deal with them later," He snarled. Four members of the Foot Clan came and dragged the wailing pig and rhino away.

"Hello, Karai. Do you remember me?" Shredder whispered to the trembling snake. Silence.

"I am your father." Still silence.

"I know you can talk! SAY SOMETHING OR PERISH!"

"Fa-father?" The snake hissed carefully. Shredder nodded, rubbing his hands together.

"Good, You have done well Hun. You shall be rewarded handsomely."

"Thank you Master Shredder. I knew I could please you."

* * *

**Ooh! I love suspense! I honestly don't have much to say so...**

**Wolf out...**


	7. Chapter 7

**Hey guys, I want to just say that I was hoping more people would see this coming! Only one person did!**

**Reviewers:**

**StarTraveler: Well you'll have to keep waiting because that won't exactly happen! At least not in the way you think!**

**DP fanboy: Yeah he is, but not the way you'd expect. Also what do you mean by spoiling? I'm not trying to be annoying or anything, I genuinely want to know so that I can fix it. And some things I like to consider _foreshadowing._**

** Dr. Guest: You'll just have to keep reading to find out!**

* * *

After Hun and his henchmen left, the others went to check on Leo. The lights in his room were off and there was a lump under the covers. Raph walked forward and shook him.

"Leo! Hey wake up!" He shouted. The lump stirred.

"No...I don't...want to get up," Leo rasped, keeping the blankets over his face. His voice was hard and rough. Donnie stepped up.

"Are you ok? You sound like you're sick," Donnie pulled the blankets away from Leo and gasped.

"Bro..." Mikey whispered. In the place of Leo was a snake. Exactly like the one they had just sent away, only slimmer.

"How did...but we just saw you...you were...Karai?" Casey stuttered. The snake shook its head.

"No, no! Not...Karai! Leo!" It spoke. The others stepped back.

"But you can't be. Leo wouldn't ever, he wouldn't, Leo is our brother!" Raph growled.

"I am Leo...dudes?" The snake hissed. Mikey stumbled forward, tears running down his face.

"Leo? Is that you buddy?" He whimpered. Donnie grabbed him and tugged him back, holding him away from the snake.

"No Mikey, it's not him," Donnie warned. Mikey turned back to him and balled his fists.

"Then what do you call the other mutant we saw? What about the one we gave to Hun! Huh Donnie? How do you explain that!" He yelled. April put her hand on Mikey's shoulder.

"Mikey, calm down. For all we know, Karai can clone herself. In the meantime we should test if this even is her," April turned to the snake. "What are all of our names?"

The snake began pointing to everyone. "Mikey...Donnie..." It started.

"No. Full names," April clarified. The snake squirmed.

"Um...Michelangelo...Donatello...Raphael...April Neals...Cassie Jones?" It offered. Casey threw his hands up.

"Cassie? CASSIE? That's a freaking girl name!" He exploded.

"And my name is April O'Neal," April pointed out.

"Oh," The snake lowered its head in shame.

"So who are you really?" Raph snarled, drawing his sai.

"...It's me...Karai..." Karai muttered. She felt something cold poke into her skin and looked up to see Raph's sword at her neck. She hissed sadly.

"If you are Karai, then where is Leo?" Raph asked deliberately and slowly. Karai sighed.

"You gave him...to Shredder," She said. The blade pushed deeper until blue-black blood burbled up from under her scales. She whimpered.

"WHAT THE SHELL!" Raph screamed.

"Raph chill dude," Casey shoved him backwards, away from Karai.

"She snake-fied Leo and made us give him away and you want me to chill!" Raph spat.

"That's why you did it isn't it?" April scowled.

"That's why you turned him into a snake!" She continued. Karai looked at her with a cold look in her eyes. Those eyes that belonged to a wild animal, cunning, ruthless.

"Not at first. At first it was to show him...show him what he wanted...give him happiness...Then later things became complicated," Karai said monotonously. It was the most she had spoken so clearly since she became a snake.

"That's messed up dude..." Mikey muttered with tears still shining in his eyes.

"What will you do now?" Karai asked fearfully.

"We're going to get Leo back. And send you off where you belong. But for now, you'll stay here," Donnie sneered. He locked the windows and walked out with the others following him, locking the door as well.

* * *

Leo didn't know where he was. All he knew was that he was in a dusty grey cell. He slithered in circles, pacing. His stomach cramped and ached. _Hungry._ His venom sacks were swollen and throbbing. After another minute, he couldn't take it anymore. His head snapped backwards, then forwards at warp speed. His fangs struck the metal bars with a clang. Nothing. Now both his venom sacks and his actual fangs hurt.

He sighed, sighed because that was the only thing he could do. Snakes can't cry. He barely even knew how his transformation had happened. Leo had been stumbling and dragging himself back to the lair when a rat had crossed his path. He remembered hunger. So much hunger. And the warm, succulent smell of blood.

After that, Leo was pretty sure he black out and then...That was it. He woke up and found himself completely mutated, but just carried on to the lair. Leo stopped, he heard footsteps.

"Karai, how are you my daughter?" Shredder loomed over the bars. Leo sighed again. He didn't want to pretend to be Karai any longer. But what were his options?

"Hello father," He muttered.

"You know, I only lied to protect you. Hamato Yoshi is a corrupted man. I care about you Karai," Shredder said. Leo looked up, surprised. _How do I respond to this?_

"I care about you too father," He offered. Shredder's gaze turned cold. He stared at Leo, as if looking through him.

"That is new," Shredder said under his breath, then he got up and stiffly walked away. Leo froze. _He's on to me._

* * *

**Thanks for reading and please review! And it has finally happened! Leo is a full snake! Well I guess it really happened last chapter, but you guys didn't know it yet! I love writing this and I look forward to hearing from you all! Anyway...**

**Wolf out...**


	8. Chapter 8

**Sorry it's late**, **I was busy and I just couldn't get to update. Either way I hope you guys enjoy and review! Also, a few of you have asked me about when I update and such. With the exception of today, I try to update every Friday. Usually I succeed, I think this is only the second or third time I missed it.**

**So expect an update for next Friday!**

**Reviewers:**

**DP fanboy: Well I won't tell you because it'll be more fun for you to read it! And as much as I hate _other_ writers doing cliffhangers, I love doing them in my stories! #Sorrynotsorry**

**WOLFJADE28: Yeah...about that...you might want to avoid the first few paragraphs of this chapter then. I have taken this into consideration though, and I will do my gruesome scenes more sparingly. Mostly. I am happy you kept reading also and I really hope you like this chapter!**

**StarTraveler: You'll just have to read and find out!**

**Guest reviewer: Read the note up top! Thanks for reviewing!**

**NeverGrowingUp: Thanks! And I will definitely keep writing!**

* * *

Leo cowered in his cage, his fangs throbbing and aching. He whimpered. Something in his mind was off, he didn't know what it was, but something was off.

"Ugh..." Leo groaned. His vision suddenly blurred and went red. The pain in his mouth only intensified and he hissed loudly.

"Hello Karai," Leo vaguely saw the outline of a fly. He heard the cage door open and he froze. Froze because he knew exactly what was about to happen. Without control, he lunged at the fly. It tried to turn to fly away, but Leo's powerful jaws clamped down on its wings.

Instantly, the scent of blood filled his nostrils but before he could rip off the wings, another scent hit him. It was the scent of fear, sadness, panic. Leo's mind snapped back into reality.

"No...I'm sorry...I'm sorry..." Leo uttered. He spit out the leathery wings and backed further into his cage. Footsteps sounded down the halls. The Shredder's shadow fell over his bleeding employee. He looked down at Leo.

"I had doubts about you Karai. But I see that you are still my daughter at heart. However, save your killing for your human form," Shredder praised. Leo blanched. Shredder opened the cage door wider and led Leo out.

_What did I just do...?_ Leo followed the Shredder blindly, wishing he was at the lair, with his brothers. Eventually they came to an enormous laboratory. In the middle of the room, a metal vat took up most of the space. Suddenly an acidic stench assaulted Leo's nose. He looked up.

The vat was filled to the brim with a stinking, bubbling, mutagen. Suddenly Leo knew why he was here.

"Isn't this magnificent Karai? Today you will finally return to your true form!" Shredder waved his hands around.

"No!" Leo shouted. Everything seemed to stop. Even the buzzing of machines sounded dulled compared to Shredder's glare. He strode closer to Leo.

"What did you say?" He asked, but to Leo it sounded like a threat.

"No..." He repeated, quietly.

"Like I said, I had doubts about you..._daughter,_" Shredder growled. Leo gulped.

Just then, Tigerclaw walked in.

"Master Shredder, the pig and rhino have been taken care of."

"Good work Tigerclaw. I will see them shortly," Shredder said. Tigerclaw nodded and started to leave, but Shredder's voice stopped him.

"Tigerclaw."

"Yes Master Shredder?"

"This is not my daughter," Shredder announced. Leo's heart almost stopped. Tigerclaw nodded, and grinned. A whirring sound started up, the world flipped upside down and Leo felt himself suspended in the air.

A thick metallic wire with a claw was holding Leo up by his tail. He squirmed and hissed but the claw was slowly moving over the vat of mutagen. Shredder sighed sadly, then regained his dark composure.

"So...Now we will see who you really are," Shredder snarled.

"No...stop...ssssshhhhhh!" Leo's tongue felt too big for his mouth, he couldn't speak. He tried again.

"Sssssssshhhhhhhh!" Leo started to panic. He couldn't talk. He couldn't talk! And now he was dangling over a substance that he could only hope would turn him back into a turtle.

* * *

"Where is Shredders lair?" Donnie interrogated Karai.

"I told you I don't...I don't..." She trailed off. Her tongue felt impossibly big.

"Ssshhh!" She hissed. Donnie stepped back.

"Sssssorry. My mindssssssss. Turningsss..." She said.

"Hmm...Interesting," Donnie mused.

"Hey Don, we need to leave!" Raph shouted.

"She doesn't know where it is!" He yelled back.

"Can't she just sniff him out?" Mikey asked. Everyone turned to look at him.

"He'ssss rightsssss!" Karai said, dumbfounded.

"Mikey you're a ge- Well...good idea Mikey," Raph complemented.

"Come on!" Donnie shouted. Karai lifted her snout and she caught a whiff of snake. Her eyes closed as she inhaled and she began leading the group through the lair and into the sewers.

* * *

"Are we there yet?"

"NO MIKEY!" Raph huffed. Casey and April were laughing in the back, much to Donnie's annoyance.

"Now?"

"NO!"

"Just asking..." Mikey muttered.

"Well stop it," Raph growled.

"Waitssss. He is nearssss," Karai hissed.

In front of them, just a few blocks away, was a grey, stone building. It didn't look very frightening with its flat, rectangular shape.

"Hang in there Fearless," Raph said. Mikey was a his side.

"We're coming bro."

* * *

**Here it is! I hope you guys enjoyed and I'm sad to say that this story might only have a handful of chapters left. Anyway...**

**Wolf out...**


	9. Chapter 9

**Okay, this chapter gets a little wild so hold on tight!**

**StarTraveler: Yeah, I would hate to be Leo right now. As for everything else, you'll just have to keep on reading! **

**WOLFJADE28: Your welcome! And thanks! I'm glad you like the story!**

**Guest: Lol. That's awesome! I've had that happen to me about two times in a row! Except I would finish reviewing a chapter, refresh my FF page, and the next chapter was up!**

* * *

"Okay, you guys go make sure it's clear," Raph commanded. Donnie and Mikey went down to the front of the building and ran to the side of it with ninja stealth. Mikey started waving his arms and kicking his legs like a headless chicken.

"Um..." Casey trailed off beside Raph. Raph shook his head and sighed.

"It's Mikey talk for: everything's clear," He clarified. "Lets go."

Casey, Raph and April inched down to Mikey and Donnie.

"We ssssshouldn't be here..." Karai hissed from behind them.

"Yeah well you should've thought about that before you dragged Leo into this!" Raph growled. She lowered her head.

"Guys, in here," April gestured. She squeezed through a doorway and the boys followed. It was quiet inside, and dark. Long, black corridors stretched in an endless labyrinth. The tiles were old and cracked. Slimy black mosses curled out from the walls and ceiling.

"Whoa...sick..." Mickey whispered, running a hand over the moist walls. Parts of the roof were knocked in and gray sunlight filtered into the hallway.

"This must have been abandoned for a long time," Donnie said. They continued traveling through the old building. After a while, a scraping, creaking sound filled the air. They started moving towards it.

April moved over by Donnie.

"What's wrong?" She asked him. She could sense that he was thinking about something.

"I don't know...just...well..."Donnie struggled. April listened.

"Well what?"

"Well, if this is the Shredder's lair...isn't it too easy? I mean, there weren't any guards or anything. And now we're just walking around his place!" Donnie sighed in frustration.

"You don't think..."April trailed off.

"GUYS LOOK OUT!" Casey screamed. Suddenly, April and Donnie felt themselves falling.

"Oomph!" Donnie grunted as he fell to the floor and felt April land on top of him. They looked up to see Raph, Casey, and Mikey staring down at them from above. April stood up and started trying the sides of the pit they were in. Smooth and steep.

"You guys go ahead!" April shouted. Mikey looked to Raph, who nodded.

"We'll be right back!" Mikey reassured.

* * *

Raph hated to leave April and Donnie behind, but Leo was the main priority. As the trio walked, the creaking noise only increased. It was silent. A whoosh of air rushed past Raph's face. He looked back and didn't see Mikey or Casey.

"MIKEY! MIKE! CASEY!" Raph yelled. No one answered.

"Dang it!" He growled. "Hey...where is-" He never got time to finish his thought before a high-pitched sound filled the air. Raph looked down and saw a green-blue gas filling the space. He fell to his knees and everything went dark.

* * *

Leo was scared. There was no other word for it. He was completely and utterly petrified. Tigerclaw and Shredder stared up at him and his stomach clenched into a cold fist. There was only one thing to do.

"Shredder! Stop! You're right! I'm not Karai! It's...It's...Leonardo. Splinter's son..." He shouted. Or at least he tried to. All that came out was a hiss.

"Drop the crane," Shredder commanded. Tigerclaw walked to a giant lever and pulled it down. Leo felt himself being lowered, closer and closer to the mutagen. He whimpered.

"Ssssssstop!" Another hissing joined the clamor of sounds. Everyone turned to see a duplicate snake, poised in the doorway.

"Put him down Fathersssss!" It snarled. Shredder straightened.

"Is that...is that really you? Karai?" He asked. The snake nodded. "Then who is that!" Shredder roared.

Karai looked over to Leo, who was still slowly sinking.

"Leonardo."

"Hamato Yoshi's son? Why is he here!" Shredder sneered.

Karai said nothing.

"Fine then. If you won't speak to me, then you can say goodbye to the turtle!" Shredder said. He ran to a wall and slammed down a large, red, button. A buzzing sound entered the air. Shredder ordered Tigerclaw to grab Karai and they ran out of the lab.

Leo dangled closer and closer to the pungent sludge. The walls started shaking and rumbling. Leo felt a wave of heat singe his scales. He choked and gasped on the thick heat, but he couldn't get enough air. The large vat started boiling. The slimy ooze, sloshed over the sides, popping and bubbling with a puss-like stench. Leo retched.

And then everything was in slow motion. A bubble started forming on the top. It grew and grew. Leo sank. The room shook. The claw holding him released. He fell. The bubble erupted into a massive explosion. Leo felt into the stinging substance, encompassed on all sides by walls of mutagen. His skin peeled and ached.

Everything went white and quiet.

* * *

**There you have it! Thanks for reading and reviewing! Anyway...**

**Wolf out...**


	10. Chapter 10

**HAPPY SUMMER VACATION! Yay! Okay so I decided to be kinda mean and delay Leo's appearance as much as possible! Besides, I had to tell you guys what was happening to the others. Enjoy! **

**Reviewers:**

**DP fanboy: Yes, yes he did! XD**

**StarTraveler: Haha! Yeah, poor Leo is right! I can't wait to see what you think of this chapter! **

**WOLFJADE28: No, I always say 'wolf out', after every chapter! LOL! Oh and about hurting Leo or Karai...well...I'll just let you read the chapter! But don't worry, there's a 50% chance I'll write a relatively happy ending! Of course, there's also a 50% chance I won't!**

**Shiego627: You'll find out! I update every Friday, but I might do more since it's Summer. Thanks for reviewing and I hope you continue reading!**

**Guest: Thanks! I can't wait to see the new episode as well!**

* * *

April was standing on top of Donnie when the entire building started shaking. She was just about to get to the top of the pit. Almost there. And then boom! She fell onto Donnie and covered her face. The ceiling creaked and groaned, pieces of rubble beginning to drop.

Masonry and dirt caked the bottom of the pit, pummeling April and Donnie. Vaguely, Donnie saw Shredder running with Tigerclaw, who was holding a snake. His stomach squeezed into a fist. Who was it? Leo? Karai? Which one!?

He was Leo's brother! He should have been able to tell! Which one was it! He was about to scream out when a piece of rock slammed into his temple. Donnie slumped over, leaving April to huddle beside him, hoping for salvation.

* * *

Raph had just woken up along with Casey.

"Whoa...that stuff musta been strong. I can still feel the room spinning!" Raph slurred.

"Yeah, me too. Weird," Casey observed. Suddenly a boulder dropped down between them with a crack. Raph and Casey looked at each other.

"You saw that too right?" Raph asked. Casey nodded. "Which means that this room is actually shaking, isn't it?"

"Yup," Casey agreed.

"Oh, ok...RUN!" Raph shouted. He puled Casey up and they started sprinting through piles of rubble. The floor tilted and slanted haphazardly. Raph was only thinking about three things: Leo, Donnie, April. They were still somewhere in this place, without him. And that meant they were in danger. His breath came out in short gasps.

"We need to find the others!" Casey voiced Raph's thoughts.

"I know! Come on!" He yelled back. They sped up, rocks falling down all the while. Casey yelped as one fell on his foot. But he limped onwards.

* * *

Karai was being held around her waist by large, meaty paws. She tried to bite into Tigerclaw but his fur was thick and coarse. She spit.

"Let meeesss go!"

"Hush Karai! We will find a new lair, make more mutagen. I will help you my daughter!" Shredder yelled. Karai squirmed.

"HELPSSS!"

"Shut up stupid girl!"

"Please! Father! We need to go back! Leonardo'sss ssstill in there!"

"I know! That is the point!"

"HELPSSSS!"

"Master Shredder, if you could make your daughter be quiet please?" Tigerclaw interrupted.

"Not a sound Tigerclaw! Not a sound!" Shredder hissed.

They ran through the hallways and barely avoided falling stones. The walls shook and heat started coming off the surfaces. Karai hissed and spat, writhing in the burning air.

BANG! Shredder and Tigerclaw ran into Raph and Casey.

"Another turtle?" Shredder snarled. Raph drew his weapons and Casey busted out his hockey sticks.

"Where is Leo?" Raph shouted.

"He's dead," Shredder laughed.

"What-NO! No he isn't!" Casey and Raph screamed.

"Try me turtle and weak human ally," Shredder rasped. Tiger claw moved backwards and Raph, Casey and Shredder attacked each other. Raph slashed at his mask while Casey pummeled him.

"Help meesss!" Karai yelled.

Casey flipped over Shredder and engaged Tigerclaw. Tiger scratched at him with his free paw, but Casey dodged. He twirled and shot a hockey puck into Tigerclaw's mouth. Tiger choked and gagged, releasing Karai. Finally the puck shot out of his throat and he roared.

As the two fought, Casey spoke to Karai over the sound of falling rocks.

"Where's Leo?" He yelled. She shook her head.

"He'sss back in the lab!" She hissed.

"How do we get there?"

"That waysss" She gestured to another hallway. Casey nodded.

"Raph! Come on!" He shouted. Casey threw down some smoke bombs and the threesome ran out.

* * *

Leo was floating. Suspended in green sludge. He felt nothing, saw nothing, heard nothing. His lungs could have exploded and he wouldn't have known. There was no longer any need for air. Something in his mind flickered. A thought. _Am I dead?_

He wondered about that. Should he be worried? Should he try to move? Open his eyes? But the liquid was so warm and embracing. He wanted to welcome it. He couldn't remember the last time he'd been so relaxed. Shivers ran down his back in pleasant tingles. Leo smiled, encompassed in bliss.

Suddenly he felt the void around him ripple. He frowned at the disturbance. All at once, tiny currents began buzzing around him. His eyelids fluttered, then opened.

His eyes immediately started burning and stinging. But he stayed down there. His vision was murky and short, but he didn't mind.

"LEEEEOOO!" Someone was shouting something. Leo stirred. _What are they saying? Who are they talking about?_

"Guys! He's in here!" Another voice, higher-pitched. Leo grunted. _Stop it! You're annoying me!_

"Oh. Oh no."

"Leo?"

"No way, no way!"

"No...n-no..."

Leo felt strong hands lifting him up. He squirmed but he could barely feel his weak arms and legs. His head broke the surface of the mutagen and he started shivering. Air rushed into him and he felt himself fall to a hard ground. But not only was he freezing, something was wrong. His chest was on fire. He gasped, trying to take in air, but he couldn't. Bile crept up his throat as he lay there, wheezing.

"Bro, are you okay?" Leo looked up to see some type of humanoid turtle with an orange sash around his head. Next to him, were two other turtles. One with a purple sash, and one with a red sash. Just behind them were two actual humans, a girl and boy. They all wore gloves.

"Air!" Leo gasped. Everyone else just stared at him. Leo passed out.

* * *

Donnie was scared. Terrified. He didn't want to think about what he was seeing. The thing in front of him could not have been Leo. It was the same size and height as the old Leo. But its body was almost entirely pink and squishy. It's skin secreted murky liquid and sloshed around in loose folds.

On either side of its head, were tiny gills. Its fingers were bloated and short, some even melted together. The skin on his legs was riddled with bluish scales and pristine white fangs poked out of his mouth. Donnie looked at the mouth. It was large, too wide. And curled upwards in a perpetual grin. Its eyes were black marbles.

Donnie felt tears welling in his eyes.

"It looks like some type of cross between a human, a turtle and a snake..." April muttered. Everyone nodded, and continued to stare at the creature that had once been Leo.

* * *

**Hey I was wondering if you guys would like me to temporarily change the cover to show you guys what the 'new Leo' looks like. I would probably change it back next Friday. But yeah, tell me what you want to see! Also, this is officially the longest chapter of Hearts of Mutagen! Hope you enjoyed! Anyway...**

**Wolf out...**


	11. Chapter 11

**Here it is guys! *Sob* The last chapter! *Cry* I just want to say thanks to everyone who reviewed, even if you only did it once! You guys helped make this story! Now without further ado, the final chapter of Hearts of Mutagen.**

**Reviewers:**

**Insanity21: Don't worry, this chapter won't make you wanna puke. It might make you cry though...**

**DP fanboy: Good point, but for the sake of argument, I think she was just trying to get Shredder to release her, with flattery.**

**StarTraveler: Thanks! And thanks for reviewing!**

**WOLFJADE28: Haha! Thanks for the silver lining! **

* * *

Donnie, Raph, Mikey, Casey and April lifted the unconscious Leo while Karai watched. Never uttering a word, they began carrying him out of the building. At the entrance they stopped.

"What are you doing?" Raph growled at Karai. She looked at him.

"Come withssssss youuussss?" She hissed.

"Wrong answer. You're staying with your daddy," Donnie muttered. They looked over as the building crumbled into a stone heap.

"Leoossss! Neeedsssss me!"

"Just like the other times when he needed you. And you let him down," April glared. Karai stared at them.

"Say? Goodbyyyysss?" She whimpered. They nodded reluctantly and set Leo down. Karai slithered close to him. She leaned in by where she assumed his ears were.

"Sorryyyssss. I did love youuussss. I really did," Karai whispered so only he could hear. Then, completely unknown to the team, she nipped his skin with the tips of her fangs. And with that, she disappeared into the night. The others watched her leave, and finally picked Leo up again, still wearing their gloves. No one noticed the tough green skin starting to form on his head.

* * *

"Ok, set him down over here," Donnie instructed. Raph eased Leo onto a metal table in his brother's lab. April was with them while Casey was in the living room trying to calm Mikey down with video games.

"Was that there before?" April asked. Donnie walked over and saw a rash of green skin spreading over Leo's face.

"Maybe..." Donnie mused. His eyes lit up. "Hang on!"

Donnie ran to another table and snatched up a syringe. He shoved it into Leo's arm and watched it fill up with blood. Then he squeezed the blood onto a slide, put it under a microscope and looked down.

"Guys it's moving!" He exclaimed. April and Raph looked at each other.

"What?" Raph asked.

"The blood cells are reconstructing and moving! I think they're reverting to normal! Leo might be turning back into Leo!" Donnie yelled giddily.

"Really!" April and Raph chorused. Donnie nodded like an insane bobble head doll.

"Wait, Donnie! Can you speed it up?" April questioned.

"Yes!" Donnie scurried to yet another table and grabbed a glowing liquid. He poured some on a cotton ball and swabbed it onto Leo's skin. The green crawled over to that spot.

The next hour was a frenzy of swabbing and pouring and watching until finally, Leo resembled a turtle. There was only one problem.

"He's naked!" Raph huffed. "Where's his shell!"

"It should grow back in a few days...I think..." Donnie evaluated. He could practically see smoke coming out of Raph's ears.

"YOU THINK!?"

"87 percent chance," Donnie said. April stepped between them.

"Guys?" A small voice rasped. Everyone turned to look at the makeshift bed, where Leo was struggling to sit up. April pushed him back down.

"Don't move."

"What's going on? Where is she?" He asked.

"Who?" Donnie said gently.

"Karai?"

The others looked at one another.

"She's gone, left. You're safe now," Raph offered.

"I miss her," He whimpered. April looked into his blue eyes and smiled delicately.

"I know you do Leo. Go back to sleep," She whispered. Leo succumbed to his heavy eyelids and fell into a dreamless sleep.

* * *

Karai sat in the nest she had made for two. She sighed. It was too late now, for anything. She had made a mistake, and now she was paying. At least she had been able to help Leo, not that he would ever know it had been her. Her chest felt tight, almost painful. She knew what she wanted to do.

Karai gathered a few of the discarded papers flying around the amusement park, and pulled out a pen from under a deliberately placed pile of leaves. The only gift Shredder had ever given her. It was sleek and black, tipped with a dragon head. She tried it. It still flowed across the pages like silk.

With a heavy heart, she made her way back to her nest, and began to write.

* * *

"Kee-yah! Yah! Come on Mikey! Show me what you can do!" Leo teased his younger brother as they sparred. Mikey laughed and swept his legs under Leo, making him fall and roll over into a crouch. Mikey leapt into a flying kick, only for Leo to grab his leg and toss him onto the floor.

"No fair! Rematch!" Mikey whined playfully. Leo smiled, helping him up.

"This is the fifth time I fought you Mikey. Give it up!" Leo chuckled. "I'm gonna go for a walk, I'll be back in an hour or so."

"Sure Fearless Leader, I know you're too scared to fight me!" Raph laughed. Leo grinned and shook his head, walking out of the lair. He perused the sewers for a while before going topside. This was nice. Speeding along the rooftops without noise and interruptions.

He didn't know where he was going, but eventually Leo found himself in Coney Island. A glimmer of memory sparked in his mind. The place where it all began. It had been a year now, since he'd kissed Karai by the roller coaster.

He knocked on his tough shell, which had long since grown back. He walked over to the roller coaster, and saw the remains of an old nest. _Our nest. _

He looked closer and saw a splash of white. He pulled it out and saw it was a paper. But not just any paper. _A letter?_

Leo sat down in the nest and was reminded of a younger, past Leo. One with love fresh in his heart and a snake tail. He chuckled to himself, then began to read.

_Dear Leo,_

_I write this because I have used up the last of my venom in my efforts to save you. You don't know it now, but I used the last drop of mutagen within me to turn you back. Look at yourself Leo, did I do a good job? Are you whole again? Are you the Leo I first fell in love with? I can only hope._

_I feel pain now Leo. Is this new for you? You didn't think the one who betrayed you could feel pain did you? But I do. My heart bleeds for you and for us. And for me, because I'm dying Leo. My life has been used up. I'm done. _

_I want to say I'm sorry. For what I did to you. I just hope you have forgiven me by the time you read this, if you ever do. Goodbye Leo. Never forget. I love you. Goodbye L_

The letter stopped on L. As if. As if she had...Leo sighed. He folded up the letter. She was gone. Suddenly Leo started digging through the nest. If she had sat here while she wrote. And if she had...passed. Then that meant...

"Yes!" Leo whisper-yelled to himself. Buried under the brambles and leaves of the nest, was a girl. She was pale, with short black hair that went up to a point. _She turned back. _

Her body was in perfect condition, minus the moth eaten clothing. He traced her heart shaped face with his finger. Then he leaned in and kissed her head. Just a short peck. But it was enough.

"Sleep well Karai, sleep well," Leo whispered to the motionless girl. Then he walked away with a sad smile perched on his lips. The letter tucked into his hand. _I love you too Karai._

* * *

**Now before you guys put a bounty on my head for this, I had to! I know it's cruel, but I. had. to. Sometimes the best stories involve character death! And I don't like doing the stereotypical 'happily ever after' endings just for the sake of happiness. **

**Think about it okay, hear me out. **

**-Karai turned Leo into a snake**

**-She practically fed him to Shredder**

**-She tried to replace him so she could live**

**-And she freaking wanted him to leave everything behind**

**Leo's brothers, and friends, would never EVER have trusted her enough for a happily ever after! EVER! It wouldn't have made sense. It would have seemed forced and fake! So that is my justification. Thanks for reading this story guys and make sure to review. Until next time...**

**Wolf out...**


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